Method of concentrating coating material in containers



D. G. MAGILL Oct. 18, 1960 METHOD OF CONCENTRATING COATING MATERIAL IN CONTAINERS Filed June 27, 1955 I I G 3 i i ihu Pli INVENTOR.

DONALD G. MAGILL TI'ORNEYS United States Patent METHOD OF CONCENTRATING COATING MATERIAL IN CONTAINERS Donald G. Magill, Great Neck, N.Y., assignor to American Can Company, New York, N.Y., a corporation of New Jersey Filed June 27, 1955, Ser. No. 518,067

2 Claims. (Cl. 113-120) The present invention relates to containers such as sheet metal cans and fibre containers and has particular reference to a method of concentrating a protective coating material at a vulnerable place of the can or container to protect it against leakage.

In the packaging of certain products in cans or containers, especially containers having fibre bodies, the interior surfaces are provided with a lining or coating material to protect the container against leakage. In fibre bodies a metal foil such as aluminum or tin foil is adhesively secured in place to serve as an inner liner. Bodies of this nature are frequently provided with interiorly located, encircling score lines to facilitate opening the container. To fully protect the liner against possible leakage through minute pin holes and abrasions, it is sometimes coated with a protective substance such as wax or other refusible or heat fiowable materials.

When a foil liner is used it has been found that scoring of the body blank causes the severed edges of the liner to lift and form a raised burr along the sides of the score line. These raised burrs form an open bridge or shield over the score line and thereby keep away or divert from the score line the protective coating substance when it is applied to the foil surface. Thus the score line is left unprotected and affords a ready path of seepage of the container contents into the fibrous structure of the body wall with the result that the wall is soon broken down sufiiciently to cause failure of the container.

In composite containers where sheet metal ends or closures are used on fibre bodies and permanently attached by an interfolding of flange parts on the marginal edge portions of the closures and the bodies, it is sometimes difficult to obtain a hermetic seam with the result that leakage occurs through the seam.

It is an object of the instant invention to overcome these difficulties by the provision of a method of concentrating a protective coating substance at the point or points which may be subject to leakage to protect the container against such leakage.

Another object is the provision of such a method wherein a concentration of coating substance may be readily placed in a ridge or head covering a score line so as to fully bridge over the score line and thus close it against contact with the contents of the container to protect the wall of the container.

Another object is the provision of such a method wherein a fillet of a coating substance may be readily produced to block entrance of the container contents into interstices leading into the end seam which secures the closures to the body.

Another object is the provision of such a method which is readily adapted to the protection of vulnerable points after the body is formed and in cooperation with the operation of forming the end seam flanges on the body.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawings:

Figure l is a perspective view of a sealed composite container having metal closures attached to a fibre body protected against leakage in accordance with the steps of the instant method invention;

Fig. 2 is an enlarged sectional view of the marginal edge portion of the body of the container shown in Fig. 1, prior to the flanging of the body;

Fig. 3 is a view similar to Fig. 2 showing the step of and a sectional view of apparatus for, flanging the marginal edge portion of the body;

Fig. 4 is an enlarged sectional view of the flanged marginal edge portion of the body and a closure and prin cipal parts of apparatus for uniting these container parts in an end seam;

Fig. 5 is an enlarged sectional view of the flanged marginal edge portion of the body and a closure prior to uniting in an end seam in a modified form of the instant method invention;

Fig. 6 is an enlarged sectional view showing the container parts in Fig. 5 permanently secured together; and

Fig. 7 is a sectional view similar to Fig. 6, showing a second modified form of the invention. I

As a preferred or exemplary embodiment of the instant method invention Figs. 1 to 4 inclusive of the drawings illustrate a method of protecting a score line A of a composite container B of the character primarily used for packing biscuit dough and the like products, although the invention is equally well adapted to containers for other products.

The composite container B preferably comprises a tubular fibre body C having sheet metal end closures D permanently attached thereto by an interfolding of flange parts on the body and on the closures to produce double end seams E. The fibre body C preferably is made from a one-piece blank formed into tubular shape with its side seam marginal edge portions overlapped and adhesively secured together to provide a side seam F which extends the full length of the body. One marginal edge portion of the side seam F extends beyond the seam on the outside of the body as a free flap G for opening the container. The opening of the container is facilitated by a pair of the score lines A, hereinbefore mentioned, disposed 0n the inside of the body C one adjacent each of the end closures D and encircling the body for nearly its full circumference.

The body C preferably is lined with a thin sheet of aluminum foil I (Fig. 2) which is applied to the fibre material While in the fiat and adhesively secured in place. In order to protect the container material against seepage through pin holes and abrasions in the aluminum foil J, a film K of wax or other refusible coating material is applied to the foil after the tubular body C is formed from the flat sheet. Protection of the score line A preferably is effected by a ridge Z of the wax coating material which is provided to bridge across and cover burrs Y raised by the severance of the aluminum foil J during the scoring operation.

The sheet metal and closures D preferably are made of tin plate or the like material and are formed with a countersunk panel L (Figs. 4 and 5) having a surrounding upright countersink wall M which at its upper edge merges into an outwardly extending flange N which terminates in a curled edge 0. The countersink wall L fits snugly within the marginal edge portion of the body C while the flange N and curled edge 0 are bent inwardly against the outside of the body C and interfolded with the marginal edge portion of the body to form the double end seam E as shown in Fig. 4.

In accordance with the preferred form of the instant method invention a concentration of the protective coating material K is deposited over the score line A to protect the score line against the contents of the container. In such a method, the tubular container body C having the adhesively applied liner sheet of metal foil J and score line A is first formed from a flat sheet. The interior surface of the container body is then covered as shown in Fig. 2, with a refusible or heat reflowable coating material such as microcrystalline wax or any of the refusible thermoplastic materials. This material may be applied in any suitable manner, preferably by spraying the material on the surface in a substantially uniform thickness film K. The entire inner surface of the body may be coated or if desired only that portion including and adjacent the score line A may be coated. The applied coating material preferably is permitted to dry before the next step in the method is effected.

Following the application of the coating material to the container body a portion of the coating material adjacent the score line A is swept, pushed or scraped into a concentrated mass in a position overlying the score line as shown in Fig. 3. This action usually reduces the thickness of the swept portion of the film K adjacent the score line and piles the swept-off coating material into a ridge or head Z which bridges across and covers the burrs Y on the severed edges of the aluminum foil J and thus closes and protects the score line A. The ridge or bead Z of coating material may or may not be thicker than the thickness of the film K as originally applied.

To facilitate sweeping or pushing of the coating material into a concentrated mass overlying the score line A, the coating material preferably is reduced to a flowable condition by the application of heat thereto. In some cases it may be necessary to reduce the material to a molten condition but usually a soft, fiowable condition is all that is required.

In the instant case as shown in the drawings, this concentration of coating material over the score line A to protect it against the contents of the filled container preferably is combined with the formation of an outwardly extending flange T (Fig. 3) on the body C in its marginal edge portion for cooperation with the flange N on the end closure D in producing the end seam E which secures the closure to the body. One form of apparatus for effecting these steps is disclosed in Fig. 3 and comprises a movable head 21 having a plug 22 which is insertable into the open end of the body C and a collar 23 having a depending skirt 24 which is adapted to surround the marginal edge portion of the body in radially spaced relation thereto.

The outer periphery of the plug 22 is stepped, beginning at the top with a downwardly and inwardly tapered flanging face 26 (Fig. 3) which at its lower edge merges into a vertical cylindrical sweeping face 27 of a diameter substantially equal to the inside diameter of the container body C. The cylindrical sweeping face 27 terminates at an inwardly disposed, preferably tapered sweeping shoulder 28, located a predetermined distance down from the top of the head 21 so as to be positioned just above the score line A when the plug 22 is fully in the container body C as shown in Fig. 3. The sweeping shoulder 28 merges into a vertical cylindrical clearance face 29 having a clearance diameter slightly smaller than the inside diameter of the film K of coating material on the container body C. The cylindrical clearance face 29 terminates in a tapered nose 31 to facilitate entrance of the plug into the container body.

The plug 22 preferably is heated to a temperature slightly above the melting point of the coating material, by an electric heating element 34 imbedded in the plug. The element 34 is connected by wires 35, 36 to a suitable source of electric heating current.

The collar 23 is connected to the top of the plug 22 with its skirt 24 extending down around the upper tapered flanging face 26 in radially spaced relation thereto.

Hence when the head 21 is applied to the marginal edge portion of the container body C, the heated plug 22 moves down into the body with its upper cylindrical sweeping face 27 snugly fitting in contact with the refusible coating material thereon. As the plug 22 moves into the body C its tapered flanging face 26 expands the marginal edge portion of the body to produce the body flange T. Simultaneously with this action the heated cylindrical sweeping face 27 of the plug at least partially melts or reduces the film K of coating material to a soft or flowable condition and the sweeping shoulder 28 pushes, sweeps or forces a portion of the soft coating material forward or inwardly with the inward movement of the plug 22 until the outwardly expanding flange T engages the skirt 24 on the head collar 23. This arrests further movement of the plug 22 into the container body C and thus stops the sweeping shoulder 28 in a position immediately adjacent and above the score line A in the body so that the soft coating material scraped off the inner face of the body and carried forward by the shoulder 28 is now in a piledup position covering over the score line A and the burrs Y of the severed edges of the aluminum foil I.

When the head 21 is withdrawn from the container body C the piled-up soft coating material remains behind and solidifies as a ridge or head Z of at least suflicient thickness to bridge across and seal the score line A and the burrs Y so that they are protected against infiltration of the container contents after filling.

Following these steps in the method, the end closure D is applied to the flanged container body C with the countersink wall M of the closure disposed within the body as best shown in Fig. 5 and secured in place by an interfolding of the body flange T and the closure flange N as shown in Fig. 4. This preferably is effected in the usual manner by a conventional seaming or closing head which includes a chuck 41 (Fig. 4) which fits within the countersink wall M of the closure D and one or more seaming rollers 42 which are rotated around the outer edge of the closure flange N to bend it inwardly, with the body flange T, against the outer surface of the body to produce the end seam E.

Where scores lines A tobe protected are disposed at both ends of the container as shown in Fig. l, the above operations may be performed on both ends at the same time or on each end separately, as desired.

In a modified form of the invention as disclosed in Figs. 5 and 6, the concentrated mass of the coating material is positioned at the base of the countersunk panel L, instead of at a score line A, to provide a circumferential seal between the inner face of the container body C and the adjoining countersink wall M of the closure D to prevent leakage through the end seam E. This is effected in the same manner as explained above in connection With the protection of the score line A. In this modified form the ridge or head Z of temporarily fiowable or remelted coating material is left a predetermined distance X (Fig. 5) down from the top edge of the container body C so that when the closure D is applied to the body and secured thereto by an interfolding of the body flange T and closure flange N to form the double seam E, the outer peripheral edge of the countersunk panel L engages against and pushes into and thus embeds itself in the ridge or bead Z of coating material and thus effectively seals the interstice, if any, between the aluminum foil I and the countersink en-d member wall M.

Where both seals are desired, at the countersink panel L and at score line A, the score line A is positioned in the container body C so as to be closely adjacent the countersunk panel L as shown in Fig. 7. Hence the ridge or bead Z of coating material may be concentrated in such a position, by the same method steps as outlined above, as to seal the score line A and the interstice between the foil J and the countersink wall M of the end closure D simultaneously and in a single operation.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the steps of the method described and their order of accomplishment Without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the method hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. The method of sealing an open circumferential score line in a tubular fibrous wax lined container body against infiltration of container contents, While flanging said body, comprising telescoping the body over a heated and outwardly flared die medium having an annular shoulder thereon to reduce the applied wax lining to a flowable condition, simultaneously peripherally sweeping said wax longitudinally of said body by means of said shoulder to build up a concentrated annular mass of wax over and covering said open score line on the interior surface of said body to prevent subsequent infiltration of the contaianer contents into said body through said score line, and peripherally flanging outwardly the end of said tubular body by means of said flared die medium as an incident to the wax sweeping operation and prior to separating said die medium from said tubular body for the double seaming of a metal end member thereon.

2. The method of sealing an interior circumferential score line in a tubular fibrous container body against infiltration of container contents, while flanging an end of said body, said scored tubular body having an inner lining of metal foil provided with a wax G 5 30 6 through which said score line extends, comprising telescoping the body over a heated and outwardly flared die medium having an annular shoulder thereon to reduce the applied wax lining to a flowable condition, simultaneously peripherally sweeping a portion of said wax coating longitudinally of said body by means of said shoulder to build up a concentrated annular mass of wax disposed over and covering said score line on the interior surface of said body including the scored portion of said metal foil lining to bridge and conceal upstanding burrs on the latter, and peripherally flanging outwardly the end of said tubular body by means of said flared die medium toward the conclusion of the wax sweeping operation and prior to separating said die medium from said tubular body for the double seaming of a metal end member thereon.

References Cited in the file of this patent UNITED STATES PATENTS 2,633,095 Magill et a1. Mar. 31, 1953 

